1. Field of the Invention
The invention relates to an autonomous mobile device, more particularly to an autonomous mobile device whose movement can be properly plotted.
2. Description of the Related Art
Generally, operation of a wireless autonomous mobile device (such as an automatic lawnmower, an automatic floor scrubber, etc.) on a surface is powered by a battery attached to the autonomous mobile device. When the battery becomes low on power, the autonomous mobile device must be returned to a base station, which may be connected to a household power outlet, so as to recharge the battery.
Conventionally, a number of ways can be employed to direct the autonomous mobile device back to the base station. For example, the autonomous mobile device may be configured to randomly travel on the surface and actively search for a beacon signal sent from the base station. When the beacon signal is detected, the autonomous mobile device may subsequently move toward the base station accordingly.
In the cases where the base station is placed by a wall surface, the autonomous mobile device may also be configured to search for the wall surface using a collision detector, and to move along the wall surface until the base station is reached.
The autonomous mobile device may also be configured to continuously capture images of the surface along a traveled path, and when it is to return, the autonomous mobile device is configured to reverse and move along the traveled path backward backwardly, in order to return to the base station.
It can be seen that however, each of the abovementioned ways for returning the autonomous mobile device to the base station does not necessarily enable the autonomous mobile device to return through the shortest, or a relatively efficient path. Since the battery may be already low when the autonomous mobile device is returning, returning through an ineffective path may add to the risk that the battery of the autonomous mobile device is depleted during the return trip, resulting in the autonomous mobile device being unable to return to the base station.